A semiconductor device disclosed in, for example, Patent Literature 1 which has a configuration in which a first conductive member (second metal plate) is disposed on one surface side of a semiconductor chip (semiconductor element) via a metal member (block body), and an electrode provided on one surface and the metal member are connected by first solder while the metal member and the first conductive member are connected by second solder is known.
The semiconductor device also includes a second conductive member (first metal plate) on a rear surface side of the semiconductor chip opposite to the one surface and an electrode provided on a rear surface and the second conductive member are connected by third solder. The semiconductor chip is encapsulated in an sealing resin body (mold resin). One surface of each conductive member on an opposite side to the semiconductor chip forms a heat dissipation surface exposed from the sealing resin body. Hence, the semiconductor device has a double-sided heat dissipation structure capable of dissipating heat of the semiconductor chip toward both surfaces.
According to the configuration in which the metal member is interposed between the semiconductor chip and the first conductive member as described above, the first solder disposed between the semiconductor chip and the metal member may possibly wet and spread along a surface of the metal member and flow into the second solder during reflow soldering. Conversely, the second solder disposed between the metal member and the first conductive member may possibly wet and spread along the surface of the metal member and flow into the first solder during reflow soldering.
In such a case, one of the first solder and the second solder is increased above a desired amount and the other solder is reduced below the desired amount. A variance in amount of solder as above may possibly give rise to inconveniences, such as a solder short circuit caused by an increased amount of solder, a shorted solder life caused by a reduced amount of solder, and contamination of production facilities caused by solder that has overflowed.
Thermal stress is known to increase when the first solder and the electrode produce an obtuse angle in comparison with when a produced angle is an acute angle. For example, in a case where the second solder flows into the first solder and an amount of the first solder increases, cracking may possibly occur in the electrode due to thermal stress.
In particular, the semiconductor device having the double-sided heat dissipation structure described as above includes a radiator on each surface side and it thus becomes necessary to manage a distance between the two heat dissipation surfaces. For a purpose of distance management, reflow soldering is performed by using a slightly larger amount of the second solder in order to absorb irregularities among respective components in height in a thickness direction of the semiconductor chip. Accordingly, the second solder may possibly wet and spread along the surface of the metal member and flow into the first solder during reflow soldering. That is to say, the first solder and the electrode on the one surface may possibly produce an obtuse angle.